1. Field of the Invention
The present invention relates to burner apparatus and method for combusting air and fuel characterized in that the fuel is thoroughly mixed with combustion air in a manner so that resultant combustion is complete and oxides of nitrogen (NO.sub.x ) in the exhaust gas are substantially reduced. "Fuel" as used herein means gas and/or liquid fuel.
2. Description of the Related Art
Combustion is a chemical process in which an oxidant is rapidly reacted with a fuel to release chemically stored energy as thermal energy. This thermal energy is usually in the form of high temperature gases. Most commonly, the oxidant for combustion is oxygen in the air. Hydrocarbon gases principally consist of hydrogen and carbon compounds and the complete combustion of these gases produces mainly carbon dioxide and water. When the combustion of air and fuel is produced at a high temperature, oxides of nitrogen (NOx) are produced due to dissociation of the molecular Nitrogen. Oxides of nitrogen gases are considered to be an environmental hazard.
In all burners, there will be regions of reactant mixture where either combustion will be incomplete or the formation of NO.sub.x will occur. Ideally, it is desirable to provide a completely homogeneous mixture with the ratio of the reactants suitably balanced to effect the best achievable combustion byproducts for a given application.
Conventional methods of mixing the fuel and air generally provide a mixture gradient through the cross section of the flamefront at the point of ignition that causes a corresponding thermal gradient through the flame. This causes both the production of NO.sub.x within the higher temperature (Stoichmetric) sections of the flame; and Carbon Monoxide, Aldehydes, Ketones and Unburned Combustibles within the colder sections of the flame (i.e., sections comprising excessive fuel and sections comprising excessive air).
Where conventional methods of producing exceptional results with respect to low NO.sub.x s have succeeded, they have generally paid for said results with any combination of the following: (1) the need for relatively high combustion air blower pressure necessitating an increased consumption of electricity; (2) relatively elevated fuel pressure requirements; (3) the recirculation of cooled flue gases to absorb enough of the heat from the initial combustion zone to prevent NO.sub.x formation; and/or (4) the inability to extend the performance through a wide range of turndown.
The present invention relates to an apparatus and method for hydrocarbon and other combustibles fuel burners to provide means for controlling the mixing of the reactants and thus, controlling the nature of the combustion kinetics. In another aspect, this invention relates to a novel method and means for limiting the production of thermally produced Nitric Oxides (NO and NO.sub.2 or "NO.sub.x "), and other unburned combustibles, in general combustion systems and heating applications.
Thus, to provide for the complete combustion of the fuel in a more economical manner while reducing NO.sub.x, CO and all other undesirable organic compounds, a better method and apparatus of mixing the reactants is desirable.